The two streams meet at a confluence. It takes many tributary streams to form a river. A river grows larger as it collects water from more tributaries. Streams usually form rivers in the higher elevations of mountains and hills. The areas of depression between hills or mountains are known as valleys.
The world's fastest production single piston engine aircraft produced in Great Britain, deployed from 1945 to 1953. Heavily Modified Sea Fury aircraft can be seen today as air racers. Heinkel He-162 562 mph. Arguably the fastest WW II jet fighter.
Image: Nasa. In a fascinating piece about the SR-71 Blackbird, the BBC calls it The Cold War's ultimate spy plane. The Blackbird is the world's fastest plane capable of speeds reaching 2,200mph (3,540kph) while its futuristic shape and black paint full of radar-absorbing iron made it virtually undetectable. The SR-71, built by Lockheed, served with the US Air Force from 1964 to 1998.